Kennith, It is difficult to be 100% sure but it appears there were two William PADFIELDs born in Somerset around the same time

I think the one who was a convict to Tasmania is the following

There is a baptism for a William PADFIELD on 31st May, 1807 in Kilmersdon, Somerset England, father William, mother Mary. KILMERSDON fits in with the convict's native place in message No. 2. So it would seem that there were two William PADFIELDS baptised in the Bath area.

Your William PADFIELDs parents were listed as John & Mary on his death so unless that is incorrect it appears he was not a convict

If we could find his marriage to Margaret it might help but there is absolutely nothing on the BDM Indexes in Victoria - I was hoping if we could get a copy of his marriage it would help but we cannot find it

Either he just said he had married & didn't or the record may be missing from the indexes as it was an early date

I don't know where else you could go with this one without further information